The present invention relates to apparatus for inserting an intraocular lens (IOL) into an eye. More particularly, the present invention relates to an insertion apparatus having a hollow tube through which an IOL is pushed with a push rod into an eye in a highly controllable manner.
The human eye is susceptible to numerous disorders and diseases, a number of which attack the crystalline lens. For example, cataracts mar vision through cloudy or opaque discoloration of the lens of the eye. Cataracts often result in partial or complete blindness. If this is the case, the crystalline lens can be removed and replaced with an intraocular lens, or IOL. An IOL may also implanted in the eye to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains.
IOLs often include a disk-like optic, and preferably at least one flexible fixation member or haptic which extends radially outward from the optic and becomes affixed in the eye to secure the lens in position. The optic normally includes an optically clear lens. Implantation of such IOLs into the eye involves making an incision in the eye. It is advantageous, to reduce trauma and speed healing, to have an incision size as small as possible.
The optics may be constructed of deformable biocompatible materials such as silicone polymeric materials, acrylic polymeric materials, hydrogel polymeric materials, and the like. The deformable materials allow the IOL to be rolled or folded for insertion through a small incision into the eye. A substantial number of instruments have been proposed to aid in inserting such a foldable lens in the eye. In a popular apparatus, the optic begins in the shape of a taco and is pushed through a gradually narrowing lumen of an insertion cartridge, progressively rolling into a tubular shape to fit through the incision. Such an exemplary insertion system is disclosed in Makker et al., U.S. Pat. No. 5,942,277, the contents of which are expressly incorporated by reference herein.
In the folding IOL insertion devices such as disclosed by Makker, et al., the cartridge is a disposable polymeric item that is held within a bore of a larger handpiece. A plunger rod associated with and arranged to travel through the handpiece bore has a distal end that lines up with a proximal end of the cartridge lumen and thus can be advanced therethrough. The distal tip contacts and urges the IOL through the cartridge lumen. Various plunger rod tips are known, some pushing on the proximal edge of the IOL optic and some lodging within the taco fold of the optic and “carrying” by outward compression the IOL through the cartridge. In the latter type, such as disclosed in Vidal et al., U.S. Pat. No. 5,776,138, issued Jul. 7, 1998, a soft cover or tip is provided on the plunger rod distal tip to avoid excessive damage of the deformable optic. The soft tip extends a small distance into the optic fold and at a certain linear travel becomes “trapped” therein by compression. This “trapping” of the soft tip within the optic helps control the rate of IOL insertion, and permits rotation of the IOL by the surgeon just as the IOL is released from the cartridge into the eye. The extent of trapping is related to the force required to push the IOL through the tube and the diopter power of the IOL, which alters the thickness of the optic. Therefore, the extent of trapping varies. Unfortunately, excessive trapping can tear the optic and even crack the cartridge tube.
In view of the foregoing, it would be beneficial in the art to provide an IOL insertion apparatus having a soft tip for controlling the IOL insertion rate and permitting IOL rotation which also prevents problems associated with excess trapping of the soft tip in the IOL.